JPS6398827A - Perpendicular magnetic recording medium - Google Patents

Abstract

PURPOSE:To prevent an increase in the coercive force of a high permeability magnetic layer and to increase the reproduction output of a recording medium by providing a nonmagnetic Co-Cr oxide layer between the high permeability magnetic layer and perpendicularly magnetized Co-Cr layer. CONSTITUTION:The high permeability magnetic layer (e.g.: 'Permalloy(R)' layer), the nonmagnetic Co-Cr oxide layer and the perpendicularly magnetized Co-Cr layer are successively laminated on a nonmagnetic base. The nonmagnetic oxide layer can be formed by using the same material as the material of a target used for preparing the perpendicularly magnetized layer and incorporating oxygen during sputtering. The coercive force of the high permeability magnetic layer can be decreased without increasing a spacing loss if the above-mentioned oxide layer is provided as an intermediate film. The recording medium having the high reproduction output is eventually obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to perpendicular magnetism used in the so-called perpendicular magnetization recording method, in which signals are recorded using residual magnetization perpendicular to the magnetic surface of a recording medium. It is related to recording media.

(Summary of the Invention) The present invention provides a two-layer perpendicular magnetic recording medium with high i!
By providing a Co-(:r-based non-magnetic oxide layer as an intermediate film between the iTi $ magnetic layer and the Co-Cr-based perpendicular magnetic layer), the coercive force of the high permeability magnetic layer is prevented from increasing, and the reproduction output is improved. This is an attempt to realize a highly perpendicular magnetic recording medium.

[Conventional technology]

In the perpendicular magnetization recording method, which performs recording and reproduction by magnetizing the recording layer in the thickness direction of a magnetic recording medium, as the recording density increases, the demagnetizing field becomes smaller. Since this method is more advantageous than the recording method, development is progressing toward practical application.

In particular, a perpendicular magnetization layer made of a Co-Cr alloy was superimposed on a high permeability magnetic layer made of a Fe-Ni alloy. The so-called two-layer structure perpendicular magnetization recording system has excellent recording efficiency, reproduction efficiency, etc., and is considered to be optimal for perpendicular magnetic recording.

By the way, in this two-layer perpendicular magnetic recording medium, the Gi'x characteristic of the high permeability magnetic layer, which is the in-plane magnetization layer, is important. In addition, this results in a decrease in recording efficiency and reproduction efficiency.

However, in such a two-layered medium, the two layers (
It has been found that the coercive force of a high permeability magnetic layer made of a pq Ni-based alloy increases due to the 14-layer structure.

Therefore, in order to suppress the increase in coercive force, Co-C
It has been proposed to reduce the saturation magnetization of the r-based perpendicular magnetization layer. However, if the saturation magnetization of the (:o-Cr-based perpendicular magnetic layer) is made too small, the reproduction output will still decrease.

On the other hand, in order to efficiently continuously fabricate two-layer perpendicular magnetic recording media from the viewpoint of productivity, it is necessary to continuously manufacture vertical Co-Cr-based magnetic recording media without releasing the vacuum state for depositing the high permeability magnetic layer. Preferably, the magnetization layer is deposited.

However, after depositing the high permeability magnetic layer, the vacuum L
When a Co-Cr perpendicular magnetic layer is formed without breaking the Q, the vacuum state is temporarily broken after forming the high permeability magnetic layer and the Co
It has been revealed that the coercive force of the high permeability magnetic layer increases significantly due to the two-layer structure compared to the case where a -Cr-based perpendicular magnetic layer is formed.

Therefore, as a countermeasure to this problem, a high permeability magnetic layer and a Co-Cr
It is conceivable to provide an intermediate layer between the perpendicular magnetization layers.

Conventionally, an example in which an intermediate layer is provided between a high permeability magnetic layer and a Co--Cr perpendicular magnetic layer is disclosed in, for example, JP-A-58-16933.
Although there are many such methods as described in Japanese Patent Application Laid-open No. 4 and Japanese Patent Application Laid-open No. 110329/1989, they have the following drawbacks due to their different purposes.

In other words, most conventional objectives have been to eliminate the influence of the crystal orientation of the high 13 (i-index magnetic layer) on the Co-Cr perpendicular magnetic layer, rather than to prevent the coercive force of the high-permeability magnetic layer from increasing. The objective is to improve the crystal orientation of the perpendicular magnetic layer.For this reason, a relatively thick intermediate layer is used, but since the intermediate layer causes spacing loss, the reproduction output actually decreases. Furthermore, in order to provide an intermediate layer, it is necessary to install a new evaporation tA (target) or equipment, which is disadvantageous in terms of equipment investment and productivity.

[Problem that the invention seeks to solve]

As mentioned above, studies on the reduction in reproduction output due to an increase in the coercive force of the high permeability magnetic layer have not yet been sufficiently investigated, and resolving this issue is an issue.

The present invention has been proposed in view of the above circumstances, and is intended to increase the coercive force of a high permeability magnetic layer by forming a double layer without increasing the spacing loss in a double-layered perpendicular magnetic recording medium. The purpose of this invention is to provide a perpendicular magnetic recording medium with a high reproduction output.

Another object of the present invention is to provide a perpendicular magnetic recording medium that is suitable from the viewpoint of productivity, equipment investment, etc.

[Means for solving problems]

The present inventors have conducted intensive research over a long period of time to develop a perpendicular magnetic recording medium with high reproduction output, and as a result, the Co-
By providing a Cr-based nonmagnetic oxide layer as an intermediate layer, high i! without significantly increasing spacing loss! +
The coercive force of the H-rate magnetic layer can be reduced, and this Co
-The Cr-based nonmagnetic oxide layer is made of C.

It has been found that this method has almost no effect on the degree of crystal orientation or magnetic properties of the -Cr-based perpendicular magnetic layer.

The present invention was completed based on these findings, and consists of a high permeability magnetic layer, Co-Cr, on a non-magnetic support.
It is characterized in that a non-magnetic oxide layer and a Co--Cr perpendicular magnetization layer are sequentially laminated.

The Co--Cr based non-magnetic oxide layer can be easily created by simply introducing oxygen during sputtering using the same target used to create the Co--Cr perpendicular magnetic layer.

The thickness of the Co-Cr-based nonmagnetic oxide layer is 1
It is preferably within the range of 0 to 400. If the film thickness exceeds 400, the decrease in reproduction output due to increased spacing loss will exceed the increase in reproduction output due to decrease in coercive force, and the reproduction output will actually decrease. do.

In addition, control of Co-Cr-based non-(ff-type oxide layer II) is controlled by the film deposition rate and deposition time in the Pano Senji production method, and by the film deposition rate and nonmagnetic support in the continuous production method. However, the lower limit of film thickness that allows reliable film thickness control is 10 people.

[Effect]

The Co--Cr based non-magnetic oxide layer provided as an intermediate film between the high-permeability magnetic layer and the Co-Cr-based perpendicular magnetic layer does not significantly increase spacing loss and has high magnetic permeability.
This prevents the resistance (ff force) of the magnetic layer from increasing due to double layering, and contributes to improving the power output.

Moreover, this Co-Cr-based nonmagnetic oxide layer is made of Co-Cr-based nonmagnetic oxide layer.
It is formed using the target for producing the Cr-based perpendicular magnetic layer as it is.

〔Example〕

Hereinafter, the present invention will be explained according to specific experimental results.

First, a high permeability magnetic layer (permalloy layer, thickness 0.51 Jm) and C
o -Cr-based perpendicular magnetization layer (Co -Cr layer, film to, 2
A two-layer perpendicular magnetic recording medium consisting of C
The change in the anti-hexamagnetic force of the permalloy layer with respect to the saturation magnetization of the o-Cr layer was investigated. Note that the sputtering conditions for each layer are as follows.

Permalloy layer target 7) N1tsFe+7.5M0n,s (
Values are atomic %〉Diameter 310㎽ Argon pressure 2 x 10'''Torr Input power 3 (10W substrate holder
Water-cooled substrate Polyamide film Go-Cr
Embryo target Place the required amount of Cr pellets on a cobalt plate (diameter 310 am) Argon pressure 3 X 10-3 Torr Input power 300 W Substrate holder
The water cooling results are shown in Table 1 and Figure 1. In this case,
After creating the permalloy, the vacuum state is temporarily released and the Co-C
An r layer was prepared. Moreover, Sample 5 is a single-layer film of a permalloy layer.

Table 1 From Table 1 and FIG. 1, it was found that the coercive force of the permalloy layer increases rapidly as the saturation magnetization of Co--CrN increases.

Furthermore, when a two-layer perpendicular magnetic recording medium is fabricated using a continuous DC magnetron sputtering device without releasing the vacuum state, the coercive force of the permalloy single-layer film is 0.6 (O
s), whereas the coercive force of the two-layer film (saturation magnetization of the Co-Cr layer is 320 emu/cc) is 2.1 (
It was found that the increase in coercive force was approximately 3.5 times greater than when the vacuum state was released.

Next, a Co--Cr based nonmagnetic oxide layer was formed using a 1blDc magnetron sputtering apparatus.

The conditions are as follows.

Sputtering conditions target Co-Cr (150mm x 250m
m x 15 mm) Cr ratio 22 area % Argon pressure I FIG. 2 shows changes in lI2ff and saturation magnetization of the sputtered film. The film thickness was measured using a stylus-type film thickness meter, and the saturation magnetization was measured using a vibrating sample magnetometer (VSM).

As a result, it was found that the 1-resback film became non-(n) when the oxygen pressure was increased to 2 x 10-'Torr or more.

Table 2 shows the oxygen pressure as l Xl0-'Torr, 2
Xl0-'Torr, 4 X 10"'Torr
This shows the change in the composition of the sputtered film when changing.

In Table 2, when the oxygen pressure was 2 x 10-'Torr, a composition distribution was observed in the depth direction.

In this way, a nonmagnetic Co-Cr-based nonmagnetic oxide layer can be easily fabricated by simply introducing oxygen during sputtering using the same target used to fabricate the Co-Cr layer. I understand that.

So next, i! ! A permalloy layer, a Co-Cr based non-magnetic oxide layer, and a Co-Cr layer were deposited on this +lli without breaking the vacuum state on a 50 μm thick polyethylene terephthalate substrate using a continuous DC magnetron spacing and taring device, A perpendicular magnetic recording medium was fabricated. The thickness of the permalloy layer is 0.5 μm, and the target composition is Ni++o.
, sFe+5M0a,s (values are atomic %).

The thickness of the Co--Cr layer was 0.15 μm, and the Cr content of the target was 22% by volume. These sputtering conditions are as shown above. The sputtering conditions for the Co--Cr based nonmagnetic oxide layer are the same as those for Sample 8.

According to this method, samples (Examples 1 to 5) were prepared by changing the thickness of the Co-Cr-based non-magnetic oxide layer, and a Co--Cr-based non-magnetic oxide layer was also deposited as a comparative example. Using these samples, the dependence of the coercive force of the permalloy film on the thickness of the Co--C nonmagnetic oxide layer was investigated. The results are shown in FIG.

From this Figure 3, it can be seen that even if the thickness of the co-Cr based non-magnetic oxide layer is 13, it has the effect of reducing the coercive force of the permalloy layer, and as the film thickness of the co-Cr based non-magnetic oxide layer increases, It was found that the coercive force of the permalloy layer became smaller.

Furthermore, among the perpendicular magnetic recording media produced by the above method, the thickness of the Co-Cr-based nonmagnetic oxide layer was 0 (comparative example) and 13 (example 1).

For 300 people (Example 5), the vertical coercive force of the Go-Cr layer and the degree of crystal orientation were Δθ. was measured.

The results are shown in Table 3. In addition, the perpendicular coercive force is determined by Kerr effect measurement, and Δθ. were measured by X-ray diffraction.

Table 3 As is clear from Table 3, Co −
Even if a Cr-based nonmagnetic oxide layer is provided, no decrease in perpendicular coercive force is observed, and the degree of crystal orientation of the Co--Cr layer is hardly affected.

Next, the recording wavelength was set to 10 μm, and the reproduction output of each of the above-mentioned perpendicular magnetic recording media was examined, and the dependence of the reproduction output on the thickness of the Co-Cr-based nonmagnetic oxide layer was examined. The results are shown in Figure 4.

As a result, the film J1 of the Co-Cr-based nonmagnetic oxide layer is 4
It was found that an increase in reproduction output was observed below 00 Å. When the thickness of the Co-Cr-based nonmagnetic oxide layer exceeds 400 layers, the reproduction output becomes lower than when no intermediate layer is provided. This is due to an increase in spacing loss rather than an increase in reproduction output due to a decrease in coercive force. This is thought to be because the reduction in playback output due to

〔Effect of the invention〕

As is clear from the above explanation, in a two-layer perpendicular magnetic recording medium having a high permeability magnetic layer as a base layer, Co-- By providing a Cr-based nonmagnetic oxide layer,
The coercive force of the highly advanced 65f magnetic layer can be reduced without increasing spacing loss, and as a result, it is possible to provide a perpendicular magnetic recording medium with high reproduction output.

In addition, a Go-Cr-based nonmagnetic L layer is deposited as an intermediate layer.
The t-oxide layer can be fabricated simply and economically by using the same target as the Co-Cr perpendicular magnetization layer and introducing oxygen into the spunter, and is also advantageous in terms of durability, installation costs, etc. It is.

Furthermore, even if a C(>-Cr-based nonmagnetic oxide layer is provided as an intermediate layer), the crystal orientation and magnetic properties of the Co-based perpendicular Tfi layer hardly change, and good perpendicular (magnetic properties are maintained). dripping

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing changes in coercive force of a permalloy layer with respect to saturation magnetization of a Co--Cr layer. Figure 2 shows the sputtered film J! when the oxygen pressure in the subafuta is changed. 1 is a characteristic diagram showing changes in magnetization and saturation magnetization. FIG. 3 is a diagram showing the dependence of the coercive force of the permalloy layer on the thickness of the Co--Cr nonmagnetic oxide layer. FIG. 4 is a characteristic diagram showing the dependence of the reproduction output on the thickness of the Co--Cr nonmagnetic oxide layer.

Claims (1)

[Claims] A perpendicular magnetic recording medium characterized in that a high permeability magnetic layer, a Co--Cr based non-magnetic oxide layer, and a Co--Cr based perpendicular magnetic layer are sequentially laminated on a non-magnetic support.